


Sweet Sherlock

by KittieHill



Series: Prompts [7]
Category: Sherlock (TV)
Genre: Big Brother Mycroft, F/M, Female Sherlock Holmes, First Orgasm, Masturbation issues, Mycroft is an adorable brother, No sex until Sherlock is 16, Oral Sex, Sherlock is 16 so legal in this country, Sibling Incest, Voyeurism, but incest is illegal, obviously, sherlock is so cute
Language: English
Status: Completed
Published: 2014-11-22
Updated: 2014-11-22
Packaged: 2018-02-26 13:23:06
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,562
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2653499
Author URL: https://archiveofourown.org/users/KittieHill/pseuds/KittieHill
Summary: <blockquote class="userstuff">
              <p>Sherlock climbed up onto the high mattress and snuggled down under the covers, entwining her limbs around Mycroft’s own as she got herself into a comfortable sleeping position and then pulled the covers back over her small frame. Mycroft realised that most teenagers didn’t allow their younger siblings to sleep with them, especially not sisters, but he quite liked the feeling of Sherlock’s radiating heat against his side, and he didn’t even complain about the drool which often ended up coating his fine cotton pillowcases first thing on a morning, as her thumb was sucked carelessly during a dream.</p><p>“Myc? Tell me a story?” Sherlock grinned with excitement, “You always tell the best stories.”</p>
            </blockquote>





	Sweet Sherlock

**Author's Note:**

> Was asked to do a Female Sherlock story where Mycroft has been an awesome big brother since Sherlock was little. 
> 
> Included smut later in the story, the first part is quite innocent (despite an encounter with Mycroft in the bath) 
> 
> Not Beta'd, please leave comments or requests!

Mycroft was reading in bed; something dreadfully boring but needed for his most recent school project on Chemistry. He startled slightly as the door was softly opened and a mess of dark brown curls showed itself around the edge of the doorway. Mycroft sighed and put down his book before looking at his adorable sister standing nervously twisting her teddy in her hands.

“Come on then,” Mycroft whispered, watching Sherlock’s eyes sparkle as her pyjama clad body bounded towards his double bed.

Sherlock climbed up onto the high mattress and snuggled down under the covers, entwining her limbs around Mycroft’s own as she got herself into a comfortable sleeping position and then pulled the covers back over her small frame. Mycroft realised that most teenagers didn’t allow their younger siblings to sleep with them, especially not sisters, but he quite liked the feeling of Sherlock’s radiating heat against his side, and he didn’t even complain about the drool which often ended up coating his fine cotton pillowcases first thing on a morning, as her thumb was sucked carelessly during a dream.

“Myc? Tell me a story?” Sherlock grinned with excitement, “You always tell the best stories.”

Mycroft looked at his baby sister sternly, “did you do your reading?”, _Sherlock nodded quickly bouncing her curls, “_ and your sums?” _more nodding “_ Okay then. I’ll tell you a story… There once was an evil man called Hitler and he did very bad things to a little country called Poland.”

Sherlock listened enraptured as Mycroft spoke softly about the Second World War, missing out the truly horrific parts, but leaving in enough to keep Sherlock interested. Sherlock closed her eyes and imagines the tanks crawling towards the Manor, the bombs going off around them and the family crushed into the air raid shelter along with Redbeard who would be scared, Sherlock insisted to herself that she would be brave for everybody. Mycroft’s voice dips to barely a whisper; he knew she was falling asleep and stroked her hair gently until the first purrs of a snore escaped her pink lips. Mycroft pulled himself further down the bed and cuddled into Sherlock tightly, switching off the bedside lamp and falling asleep behind her.

* * *

 

Mycroft was dozing in the bathtub lazily; softly splashing the hot water over his chest and stomach to keep himself warm in the cold winter air. The water was deeper than strictly needed and covered his chin where soft auburn fuzz had started to grow patchy over the area. Mycroft smiled to himself as he rubbed a hand over the barely-there wisps of hair, wondering how he would look with a moustache or beard; he contemplated using bubbles to make a bubble beard, like he used to do with Sherlock when she was younger but changed his mind quickly, _he’s almost a man now_.

His mind began to wonder towards Penny in his class at school; she’s not as intelligent as him, downright stupid if anything, but she’s fair and pretty with long golden blonde hair which cascades down her back in a waterfall, her dark-rimmed glasses frame her hazel eyes and her breasts… _well…_ her breasts are exquisite. Mycroft has found himself _(on more than once occasion)_ staring at her in class; watching her bend over the back of the chair to click her spine which causes her breasts to push against the fabric of her school blouse, threatening to pop the buttons with the enormous pressure of the skin against material. Mycroft always tried to be discreet but last week he had allowed his eyes to linger for a moment too long, wondering what breasts actually feel like and how they would feel in his hands ( _are they squishy? Or firm?)_ His mind hand wandered until he realised that Penny was staring at him, an upturned eyebrow and a coy smile as she looked over the evidence of Mycroft’s voyeuristic session. His erection pressed tightly against his well-cut trousers and was clearly visible under the desk causing Mycroft to attempt to cross his legs, catching his bollocks between his thighs. A high pitch yelp had escaped his lips and caused the whole class to turn around as he blushed crimson and attempted to stop himself looking guilty much to Penny’s amusement.

Mycroft wrapped his hand tightly around his cock as he lay in the tub; hot water lapping over his erection as his fingers stroked around his glans, pulling back the tight foreskin and twisting slightly with a deep groan.

“Myc?” Sherlock asks nervously, “are you okay?”

Mycroft pulled himself upright immediately; attempting to cover his privates with a sponge whilst spilling bathwater onto the tiled floor of the bathroom,

“Sherlock! What are you doing?!” Mycroft spat angrily, his heart pounding in shame.

“I heard… I heard noises and I thought you were hurt. Are you hurt?’”Sherlock asks innocently, her eyes wide with alarm.

“No,” Mycroft sighed, his face bright red in embarrassment, “I’m not hurt, I’m fine, you go to bed Sherlock and I’ll come read a story when I’m dry.”

“What were you doing?” Sherlock asks, craning her head to look at Mycroft’s partially deflated cock.

“I’m not doing anything!” Mycroft insisted too sharply,

“If you’re not doing anything, then why are you sitting like that?” Sherlock asked pointing at Mycroft’s ramrod straight spine.

“Sherlock, don’t be clever. I’m the clever one.” Mycroft snarled, “just go.”

“Is there something wrong with your whatsit?” Sherlock asked watching as Mycroft finally admits defeat and lowers his head with a sigh,

“No. Nothing is wrong with it...” Mycroft replied, attempting to think of a way to explain what he was doing, “remember last year when we read the book about sex and reproduction?”

Sherlock settled herself on the toilet seat lid and nods her head, yes, her eyes scanning Mycroft trying to figure out his problem before he admitted it.

“Well. Sometimes...” Mycroft started, clearing his dry throat, “when you get older… you get urges. Sometimes you might be thinking about something, and sometimes you might not and it just happens.”

Sherlock nodded again; her fingers coming to steeple under her chin as she listened carefully,

“So, when you have urges, your erm… penis gets full and big, and then you need to rub it to get it down again.” Mycroft clinically explained, his face still burning crimson.

“Or have sex,” Sherlock added with a smile, glad to contribute,

“Yes, or have sex but since it’s illegal until I’m 16 and I don’t have anybody to have sex with, I have to make do with rubbing it.” Mycroft sighed,

Sherlock nodded carefully; her mind whirling with new information, storing it away for future use.

“So, are you going to rub it now?” Sherlock asked innocently.

Mycroft snapped his head up and frowned, “Well… that’s none of your business, Sherlock!”

Sherlock returned the frown before trying again “whenever I need to learn about something, you teach me. So why wouldn’t you teach me about this? It’s only a body Myc… like an experiment!”

Mycroft shook his head, looking up at Sherlock’s large dazzling eyes.

Sherlock pouted petulantly and left the bathroom, Mycroft ensured that he heard the younger Holmes enter her own bedroom before he took himself back in hand, stroking himself quickly and roughly until his back arched and he came over his stomach and the warm water.

* * *

Sherlock lay in her room; she was laid in the middle of the bed on her front, her face buried in her arms as she sulked at Mycroft’s evilness. She had only wanted to get an idea of human anatomy! She had seen pictures in the books but had never seen one in real life. She sat up and decided to spy on Mycroft and try to see him rubbing himself to make it bigger.

The opportunity came a week later; Mycroft had been out in the orchards with father whilst Sherlock ran around the house looking for things to burn for an experiment. She walked into Mycroft’s room and realised that if she climbed into the wardrobe and closed the door with only a crack of light, she would be able to see all of Mycroft’s bed. Deciding that she would come back later she quickly made a space of Mycroft’s shoes and then ran from the room.

Her tummy fluttered at dinner and she didn’t feel like eating much instead, picking at her food and moving it around the plate until mummy got mad and told her to take her plate to the kitchen and go to bed without supper. Sherlock sighed and pouted as she left the table before smiling as she placed her plate on the sideboard, and ran to her bedroom. She heard Mycroft helping mummy with the washing up, so she tiptoed to Mycroft’s bedroom, and hid in her hiding spot, closing the door perfectly until it lined up with the bed. She wiggled her bum to get comfortable and waited.

About half an hour later Mycroft returned upstairs; he grabbed the pyjamas from his bed and began to strip down. Sherlock watched in awe as the muscles of Mycroft’s arms flexed as he pulled his arm above his head, the wispy chest hairs which covered the pale flesh moved down in a trail to below Myc’s trousers. Sherlock watched as Mycroft began unzipping his tailored trousers and pulling them down, folding them carefully and placing them over the back of the chair near his desk. He pressed his fingers into the waistband of his boxer shorts and pulled them down to bare himself directly at Sherlock’s stealthy position.

Sherlock pressed a hand over her face to stop the gasp. The thingy between his legs __Penis__ _Sherlock reminded herself_ _ _it’s a penis__ was small and floppy, a wormlike shape with too much skin hanging over the edge surrounded by orange hairs. Mycroft scratched idly at the hair before locking the bedroom door and lying on his bed naked, his fingers traced lazily over his nipples, pinching them slightly and watching them harden into nubs whilst his cock began to react, thickening slightly with each rub of his nipples.

Mycroft let one hand rub down his stomach into the thick hair which covered his pubic area, he had noticed that he was a lot more grown-up than some boys in the changing room, who hardly had any hair; he had a lot growing all over.

His hand wrapped around his cock and stroked gently, pulling the foreskin back over the head and enjoying the sensations as his fingers traced the glans beneath. His cock was almost at full hardness now and he stroked and fondled it happily, sighing as the pleasure rushed through his body with each stroke. He cupped his balls, feeling the strange lumps inside before moving further down to the most personal and private place. His finger softly touched the skin of his puckered hole and Myc shuddered, a bead of fluid forming at his tip which he quickly collected and rubbed around the head.

His mind wandered to Penny again, they had kissed behind the gym block. Her lips tasted of fruit and her tongue lapped at his own as he opened his lips to let her inside; she stroked his cock through his school trousers until he was sure he was going to come but she turned away and smiled, kissing him on the cheek and running to meet her friends, leaving Mycroft painfully aroused and confused. He had had to wank himself quickly in the boys toilets, finishing on tissue which was quickly flushed. Mycroft thought of Penny’s lips and tongue as he stroked his cock in bed, he imagined her on her knees sucking his cock, licking at the plentiful precome which flowed from the tip in rivers until it dripped into his pubic hairs. His orgasm hit him in surprise causing his back to arch and his breathing to catch. A moan escaped his tight lips, as his eyes rolled backwards and rope after rope of come covered his body. Mycroft twitched as his stroking slowed to a stop, squeezing the last drops from the tip he exhaled shakily before grabbing the tissue he kept by his bed. Patting himself dry he stood up and walked to the en-suite bathroom closing the door and turning on the shower.

Sherlock watched Mycroft leave and when the coast was clear, she darted from the wardrobe, unlocking the door and closing it as quietly as possible. She ran to her bedroom and locked the door throwing herself to the bed to process her findings.

Sherlock remembered the size of Mycroft when he started, it looked weird when it was floppy but when Mycroft touched his nipples and stroked it a little bit, it grew bigger and fatter. It leaked too, and Sherlock had watched as it dripped down the big bit and into the bush of hair. Sherlock had been confused about why Mycroft moved his finger down to his bum… Sherlock had always expected that to be dirty, but Mycroft had sighed softly and wrapped himself around his penis harder, pulling faster until the liquid had squirted out. Sherlock had had to cover her mouth again to stop the yelp of surprise at the explosion between Mycroft’s legs. She heard the nice sounds come from Myc’s mouth and she wondered if she could ever make Mycroft make those sweet noises.

She rubbed her thighs together and noticed they were sticky and sore, worried that she had had an accident she quickly changed to her pyjamas and snuggled into bed; storing the information away in the mind palace which Mycroft had begun to show her.

The pattern continued for years; every time Sherlock had a chance to spy on Mycroft she climbed into her hide away and watch her older brother bring himself off before rushing back to her own bedroom and touching her aching folds and budding breasts. Sherlock couldn’t understand the sensations which caused Mycroft so much pleasure, it was pleasant but nothing spectacular and she began worrying that she was anatomically wrong.

Mycroft returned home for the university Christmas holidays; he attempted to come home as often as possible to visit his sister, as he knew that his parents had been having some issues with the strong-willed Sherlock. She had become a social outcast at school due to her intelligence, and lack of social skills, insisting on experimenting in the school labs or reading in the library until she could go home where she stayed alone and sullen in her bedroom. Mycroft attempted to bring her out of her shell by bringing along the newest books or apparatus which he could find in the city as well as playing piano whilst she played along with her violin but she was still full of teenage angst and frustration. Mycroft had hardly recognised the now 16 year old female who stood before him in tight jeans, a black band t-shirt with a garish heavy metal band pictured on it and dark black kohl-lined eyelids which seemed to frame her almost colourless eyes. She had also gone out and had various places pierced much to mummy’s anger who had grounded her ( _not that Sherlock cared, she preferred being inside anyway.)_

Mycroft quickly noticed the way Sherlock looked at him; her eyes glittering in his direction and her lips flicking out to wet the perfect heart-shaped lips, all of the symptoms of a lustful teenage crush. Mycroft looked over his sister appreciatively, he had to admit that she was a beautiful woman now, her dark hair was cut short but feminine, her cheekbones protruded in a way which would make supermodels jealous and her lips were plump and could only be described as ‘kissable.’

Mycroft continued looking over Sherlock’s body, her long pale neck led to her thin shoulders. Her medium sized breasts _a C cup_ Mycroft deduced, down over the flat stomach covered with the tight band t-shirt she insisted on wearing and then to her widely flared hips and long legs. Even her feet looked dainty and feminine. Mycroft tore his gaze away as he realised that Sherlock was watching him with an upturned eyebrow, her gaze quizzical as her brother looked over her womanly curves. Mycroft could only clear his throat and turn away hoping that Sherlock hadn’t noticed the bulge growing in his trousers.

Sherlock had noticed, her mouth had dried to a parched desert as she looked over her brothers obviously aroused state, the blush of his cheeks, his heavier breathing. Sherlock needed a plan.

After a tense supper the Holmes family said goodnight and retired to their own rooms; Sherlock and Mycroft had bickered and fought throughout the meal which had caused Sherlock to stomp to her room sulkily, all planned of course, but completely normal to the parents who swiftly began complaining to Mycroft about what a bother the teenage Sherlock was becoming.

Sherlock waited for a while, her naked body draped over the silk sheets of her bed, her fingers trailing teasingly over her neck and throat, over her nipples and finally dipping to the slick folds between her legs, hoping her deductions were right… a soft knock on the door told her she was.

She didn’t answer, instead, gave a choked groan which could be taken as permission to enter. Sherlock continued to stroke and caress herself, sighs and groans escaping her lips dramatically as pressed fingers inside her aching mound; a flash of colour in her peripheral vision told her that Mycroft had entered the room. It was time for her biggest gamble.

She closed her eyes and arched her back whimpering “Oh Myc...” before hearing her brother gasp; her eyes flew open in feigned alarm and she pulled the covers over her naked body shouting “MYCROFT! WHAT ARE YOU DOING?!”

Mycroft stood in the doorway; his eyes lingering on Sherlock’s lips as she spoke. His heartbeat fast in his ears as the blood rushed to fill his very erect cock; he cleared his throat and began his explanation,

“Y-y-you said to come in.” Mycroft stuttered; he had _never_ stuttered before

Sherlock’s piercing eyes fixed on her brother before she looked down and blushed “What did you want?”

“Your behaviour was unacceptable at supper. You upset mummy.”

Sherlock feigned innocence and sighed deeply; looking at her big brother she bit her lip and apologised “I have a lot going on. I’m sorry. I’ll apologise.”

Mycroft softened slightly and moved from the door to the chair opposite the bed, sitting down and crossing his legs as best he could with an erection, “What’s going on?”

The plan couldn’t have worked any better. Sherlock’s heart thudded as she conjured tears to her blue eyes, looking at her long fingers which still had her wetness lingering on the skin before looking up at her brother, “I can’t orgasm.”

Mycroft choked slightly but recovered quickly, his face flushing as he nodded “Oh”

“I try! God I try Myc, it feels nice but it never really gets me anywhere. I feel like I’m getting close but then my brain begins thinking again and I lose the edge!” Sherlock admitted truthfully, “I’m becoming more and more frustrated.”

Mycroft shifted awkwardly in his seat “I still don’t understand why this means you have to argue with me.”

Sherlock pondered for a moment before adding “because you left. I could always come to you with things, you were the one who told me about masturbation remember? Then you left and I had to figure it out alone and I don’t think I can do it right.”

“How would I have been here helped? It’s not really something I can show you!” Mycroft said shocked.

“You could have. You could have helped me, showed me how to touch myself.” Sherlock whispered, her fingers trailing over her skin again “you always helped me with my experiments.”

“I know you used to watch.” Mycroft admitted, “the door was always unlocked and there was a Sherlock spaced gap in my wardrobe.”

Sherlock was the one to gasp now; she thought she had been so discreet,

“We’re not like other siblings are we?” Sherlock asked sadly,

“No. No, we’re not.” Mycroft admitted “but even still… I can’t touch. That’s illegal.”

“Talk to me Myc, tell me what to do...” Sherlock begged, the sheet covering her body now falling forgotten to bare her perfectly pink nipples to Mycroft’s hungry eyes,

Mycroft hesitated for half a second before sighing, “Lie down, comfortably.” Mycroft soothed, “let me see you.”

Sherlock blushed but followed the instructions, her pale skin lying out on the expensive dark blue bedding made her skin glow. The dark curls which covered her head also covered the top of her mound, although Sherlock had ensured to shave carefully to show herself off fully for her brother,

“Stroke and caress your nipples- _yes just like that –_ does it feel good?”

Sherlock nodded, her teeth worrying her bottom lip,

“Can you feel the heat pooling in your stomach? The nice sensations up your spine?” Mycroft’s soft voice lilted across the bedroom,

“Yes Myc, I need more,” Sherlock whined,

“Slowly, move your hands down, cup your mound and press your palm against your spot at the top.”

Sherlock complied, her hands moving down her skin to caress through the curls and press where Mycroft told her. Her hips flinched at the sensation but she continued grinding down on the pressure,

“Tell me how it feels?” Mycroft asked, his voice deep with lust,

“Good. Like scratching an itch but it’s not enough.” Sherlock sighed,

Mycroft smiled “okay, show me how you would normally play.”

Sherlock happily pressed a finger inside herself, feeling the heat and wetness coat her finger as she slowly thrust them in and out, her thumb brushing the nub of her clit with each pass,

“Tell me,” Mycroft whispered,

“It feels good, I’m getting closer, and I can feel the tingles spreading through my body but it’s not enough.” Sherlock strained, her fingers moving faster before she pulled out and groaned deeply, her hands tangling painfully in her hair as she pulled, “I can’t! I can’t do it, Myc!”

Mycroft soothed her before moving to sit on the bed beside her. Taking her hands out of her hair he placed them on the bedding and ran his hand over the soft skin of her stomach,

“It would have to be our secret...” he insisted,

Sherlock whined and nodded quickly; her tear-filled eyes looking up at her brother with hope as he began to roll up his sleeves,

“Do you feel aroused enough?” Mycroft asked with a coy smile, watching Sherlock glare at him “Okay okay, so you are.”

Mycroft pulled himself into the correct position before pressing his thumb softly over the sensitive nub of Sherlock’s clit, listening as Sherlock hissed with relief, her fingers tightening around the bedding. Mycroft kept steady pressure on the nub, circling it slightly with the pad of his thumb as his other hand traced over the still hard pink nipples. Sherlock’s tongue flicked out to lick her lips as the pleasure built slowly; she gasped when she felt one of Mycroft’s thicker digits penetrate her for the first time, her tight and hot hole gripping his finger.

Mycroft felt like he was going to come in his pants; the erotic nature of the scene was almost too much but he reasoned that he was just helping his sister with her problem. He would do anything she requested and this was just an intimate experiment his brain explained. Mycroft looked up at his sister with wide eyes and asked: “you’re still a virgin, sister dear?”

Sherlock furrowed her brow and looked at her brother quizzically, “of course I am.”

Mycroft pulled out slightly and pressed two fingers inside, feeling the stretch of her skin,

Mycroft soothed “just relax and I’ll help.”

Sherlock nodded and replaced her head on the pillow, feeling the sensations rush through her body as her brother worked her inside and out; shallow thrusts made tingles rush up her neck and caused her hair to stand on end. A new sensation joined the fray as something ran over her clit, something warm and wet…

Sherlock looked down between her thighs and saw the top of her brothers auburn hair, his lips pressing against the skin of her mound whilst his tongue slipped and caressed against her nub. The intense pleasure and warmth of Mycroft was enough to almost tip her over the edge, she grabbed Myc’s hair and held him close as the pressure built inside her; growing to a point of frenzy her hips bucked against his face as her breathing became ragged,

“Myc… Myc something’s happening… oh god, oh yes, yes Myc _please!”_ Sherlock screamed; her hand covering her mouth as her orgasm rushed through her body in hot waves, her eyes rolled back and her hips juddered to a stop as Mycroft began to stop his ministrations, pulling his lips away from his sister’s clit and pulling out his fingers from her insides. He grabbed his handkerchief from his pocket and wiped his face and hands before covering Sherlock’s shuddering body with the sheet. He stood up and walked to Sherlock’s head, pressing a chaste kiss on her forehead before leaving the room for his own. Sherlock fell asleep almost immediately as the afterglow washed over her, leaving her feeling like she was floating above the bed.

Mycroft locked his door and immediately undressed, leaving the clothes untidily on the floor as he took his red cock in his hand, pulling and tugging the skin harshly as he chased his orgasm. Precome had pooled in his underwear and was steadily dripping over his fist as he pulled; he lifted his fingers to his face and pressed them to his tongue, tasting the salty musk of Sherlock as he sucked, remembering her whimpers and his name of her tongue as she orgasmed for the first time. He pulled out his handkerchief and held it beneath his twitching cock, catching the ropes which spilled out almost immediately with a deep groan. His legs buckled slightly with the force and impact of the climax and he lowered himself to the bed, pulling and milking the last few drops from his cock into the fabric. His heart fluttered as he realised what happened and the act of incest the pair had committed but he wasn’t feeling guilty. Mycroft wondered how far his sister would be willing to take their new found companionship.

Mycroft found out the next night when he found Sherlock waiting in his bed; wearing a large white shirt and nothing else. Sherlock laid back on the comfortable pillows and gave Mycroft her most lusty gaze,

“Sherlock, why are you here?” Mycroft tried to ask impatiently, but it only came out breathily.

“Because brother dear, I want you.”

“We can’t.”

“We can.”

The arguments continued until Sherlock’s reasoning won; she explained that they had already crossed a barrier and the world hadn’t spun off its axis and gone hurling into the sun. The world was exactly how they left it except Sherlock wanted more of her brother and she was sure Mycroft wanted more of her.

Mycroft had to admit that he did, pulling her in for a passionate kiss


End file.
